如何捕捉最小化按钮的按下并在最小化窗体前有所操作？

可以这样截取WM_SYSCOMMAND信息:

type
TForm1 = class(TForm)
public
procedure WMSysCommand(var Msg: TWMSysCommand); message WM_SYSCOMMAND;
end;

procedure TForm1.WMSysCommand;
begin
if (Msg.CmdType = SC_MINIMIZE) or (Msg.CmdType = SC_MAXIMIZE) then
begin
// 你的代码...
end;
DefaultHandler(Msg);
end;